Alloy



Nov. 15, 1927. 1,649,094

P. H. BRACE ALLOY Filed Nov. 16. 1921 Ff 2 ,y1

Temp. l C'ombl'n'on 0f I d'c Z r/ 7 Hf. Z5. m r/ Temp.600C.

F1' 4. Ff .5; WITNESSES: 7 INVENTOR 703%. "92X 1D0/'7er Hfce.

29.5 7 I ATTORNEY Patented Nov. 15, 1927.

UNITED STATES i, 1,649,094 PATENT OFFICE.

PORTER H. BRACE, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUBE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

ALLOY.

Application. led November 16, 1921. Serial No. 515,604.

This invention relates to alloys, more particularly to a composite wire of a plurality of alloys for use as lead wires for glass vacuum apparatus, such as lamps, vacuum tubes, and the like.

In glass vacuum apparatus, such as lamps or vacuum tubes, it is necessary that lead wires pass through the glass connecting' the filaments or electrodes Within the same to an lo external source of electrical energy. In order to provide a gas-tight seal between the lead wire and the glass of the apparatus, it is essential that the coefficients of expansion of the wire and the glass be approximately l5 the same.

rIhe characteristics of the glass used in such'apparatus varies with the functions of the apparatus and generally there are used two types of glass, the so-called soft glass which has a low softening temperature, and a relatively high coeflicient of expansion and is annealed at a temperature of 300 to 400 C., and the so-called hard glass which has a low coeiiici-ent of expansion and a high softening temperature and which is usually annealed at a temperature of about G00o C.

For the low softening temperature glass, the lead wires used` generally consist of a 32% nickel steel which is covered with a copper sheath. Wire of this type functions well with soft glass but its coefficient of eX- pansion is so high that it is entirely unsuited for use with the hard glass.

Hitherto, the only material which has 35 been found suit-able for lead wires for glass vacuum apparatus embodying hard glass has been tungsten, which has a low coefficient ofl expansion of the same order as that of the glass. However, tungsten is generally relatively fragile, is expensive and difficult to produce and work. It is, therefore, desirable to provide a lead wire for hard glass having the necessary low coefficient of expansion and which is inexpensive and easy 46 to produce.

It is, therefore, an object of this invention to provide a material suitable for use with hard glass and which has a low coefficient of expansion.

It is a further object of this invention to provide a composite wire comprising alloys aving inversions to their 'temperature-expansivity relations, the combination of which provides the low coefficient of expansion desirable for use with hard glass.

In, practising my invention, I provide a wire including reversible and irreversible alloys, such as nickel steels, the wire being inthe form of a core of one ofv the alloys having a concentric shell or shells of one or more other alloys. The ratio of the diameters of core and shell is determined by the characteristics of the alloys chosen, and the nagnitude of the resultant expansion de sire A reversible alloy is one which, on heating, follows a certain curve of expansion and, upon cooling, retraces the original heating curve. An irreversible alloy is one which, on heating, follows one curve and, on cooling, follows a different curve. In my invention, I utilize the properties of both the reversible and irreversible alloys, such as nickel steels, combining the same in such proportions that the resultant contraction curve is approximately that of the glass with which said alloys are to be used.

In the accompanying drawings constituting a part hereof and in which like reference characters designate like parts,

Fig. l is a curve showing the expansion and contraction of an irreversible nickel steel alloy;

Fig. 2 is a curve showing the expansion and contraction of a reversible nickel steel alloy;

Fig. 3 is a curve showing the contraction of a composite of the reversible and irreversible nickel steel alloys, the curves of which are illustrated in Figs. 1 and 2;

Fig. I is a longitudinal cross-section of a lead wire made in accordance with this invention;

Fig. 5 is a transverse section of the same;

Fig. 6 is a longitudinal cross-section of a 95 lead wire made in accordance with a modification of my invention, and

Fig. 7 is a transverse section of the same.

When an irreversible nickel steel is heated, it follows the heating curve l shown in 100 Fig. 1 and, upon cooling, follows the curve 2, the two curves being common along the line 3. The reversible nickel steel, upon heating or cooling, follows the curve 4 shown in Fig. 2. By combining reversible and ir- 105 reversible nickel Steels, there is obtained a composite material, the contraction cooling curve 5 of which is different from the curves 1, 2 and 4 and follows rather closely the contraction curve 8 of hard glass.

I preferably provide an irreversible nickel steel alloy containing approximately 12% nickel forming a core 9 therefrom and surround the same with a sheath l0 of a reversible nickel steel containing approximately 40% nickel. rlhe outside diameter of the sheath 10 is approximately twice that of the core 9. A lead wire of this material follows the contraction curve 8 of hard glass very closely below an annealing temperature of 600 designated as point 7 onFig. 3, thus providing a material for lead Wires which induces practically no strain in the material after annealing.

In order to suitably modify the characteristics of the composite Wire, which I utilize for lead Wires for glass vacuum apparatus, I may addother elements which control or modify the characteristics of expansion thereof and their physical or Vchemical properties. For instance, I have appliedcoatings of chromium or other refractory materials, such as tungsten or molybdenum to prevent oxidation of the Wire during the glass-blowing operations and to provide a good bond between the Wire and the glass. The physical characteristics of the alloys may be modified by the addition ot various metals, such as cobalt, chromium, tungsten, molybdenum, vanadium, titanium or carbon which may be alloyed with one or all ot the component alloys of the composite wire.

Although I have described a speciic embodiment of my invention comprising a reversible and an irreversible nickel steel of certain specific proportions, it is to be understood that my invention is not limited to nickel steels nor to the proportions stated but that my invention is directed broadly to a lead Wire including alloys having inversions in their length-temperature curves. Although I have described the composite wire having a core of reversible alloy and a sheath of irreversible alloy, it is obvious that the positions of the alloys may be interchanged and that the form of the wire may be modified, as desired. For instance, I may provide a composite Wire consisting of strips sheath thereon as shown in Figs. 6 and 7 'Ihese and various other changes may be made in my invention without departing from the scope thereof.

I claim as my invention:

l. A lead Wire for glass apparatus com-` prising a plurality of layers of nickel steels, at least one ot said layers having reversible and at least one of said layers of steel having irreversible temperature-expansivity characteristics.

2. A lead Wire for glass apparatus comprising a core member and a sheath member, one ot' said members being a reversible and tpe lother member being an irreversible nickel s ee 3; A lead Wire for glass apparatus comprising a core of 12% nickel steel and a sheath of 40% nickel steel.

4. A lead Wire for glass apparatus comprising a core of 12% nickel steel and a sheath of 40%Y nickel steel, the outside diameter of the Wire being approximately twice the diameter of the core.

5. A lead Wire for glass apparatus comprising a body ot iron alloy having a reversible temperatureexpansion curve and a body of iron alloy having an irreversible temperature-expansion curve said bodies being combined into a laminated wire having a uniformly low coefficient of expansion over a wide range of temperature.

6. A lead Wire for -glass apparatus comprising a body of iron alloy having a reversible temperature-expansion curve and a. bdy ot iron alloy having an irreversible temperature-expansion curve said bodies .being combined into a laminated wire having a uniformly lowcoeicient of expansion over a Widl range'ot temperature up to about 600(J In testimony whereof, I have hereunto subscribed my name this 31st day of October 1921.

PORTER H. BRICE. 

